Ruthenium and Magnetite Intergrowths From the Loma Peguera Chromitite, Dominican Republic, and Relevance to the Debate Over the Existence of Platinum-Group Element Oxides and Hydroxides

Zaccarini, Federica; Bindi, Luca; Garuti, Giorgio; Proenza, Joaquín A.

doi:10.3749/canmin.1400030

Cited by 11 publications

(13 citation statements)

References 28 publications

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“…As can be seen in Figure , Ru–Os–Fe grains from Loma Peguera plot close to results published by Zaccarini et al. (), whereas compositions of Ru–Os–Fe grains from Loma Larga reveal a clear Fe‐enrichment trend towards the field of ruthenian hexaferrum (Mochalov et al, ).…”

Section: Mineralogy Of Fe‐rich Oxygen‐bearing Ru–os Compoundssupporting

confidence: 88%

“…The nature of these compounds has, nonetheless, remained uncertain. Recently, Zaccarini et al () analysed two Fe‐rich and oxygen‐containing Ru–Os compounds found in chromitites from Loma Peguera (Dominican Republic) using X‐ray computed tomography and X‐ray diffraction. They concluded that these grains consisted of “a fine intergrown of ruthenium and magnetite not detectable at the scale of the electron microprobe” and that desulphurisation of primary PGM (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…However, the interpretation of Zaccarini et al. () assumes ab initio that “Ru, Os, and Ir behaved like noble metals, at least during the alteration processes, such as serpentinizaton and lateritization”, thus precluding any possible PGM transformation via Fe incorporation during lateritisation. On the contrary, several authors have suggested that PGE are not inert during weathering (Aiglsperger et al., a; Bowles, ; Cabral et al, ; Garuti et al, ; McDonald et al, ; Melcher et al, ; Oberthür et al, and references therein).…”

Section: Introductionmentioning

confidence: 99%

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The supergene origin of ruthenian hexaferrum in Ni‐laterites

et al. 2017

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For two decades, the nature of Fe-rich, oxygen-bearing, Ru-Os compounds found in the supergene environment has been debated. Ru-Os-Fe-oxides and nano-intergrowths of ruthenium with magnetite have been proposed. We applied FE-SEM, EMPA, l-Raman spectroscopy and synchrotron tts-lXRD to Ru-Os-Fe compounds recovered from Ni-laterites from the Dominican Republic. The results demonstrate that a significant portion of Fe exists in a common structure with the Ru-Os alloy, that is, ruthenian hexaferrum. This mineral occurs both as nanoparticles and as micrometric patches within a matrix of Fe-oxide(s). Our data suggest that supergene ruthenian hexaferrum with a (Ru 0.4 (Os,Ir) 0.1 Fe 0.5 ) Ʃ1.0 stoichiometry represents the most advanced weathering product of primary laurite within Ni-laterites from the Dominican Republic.

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Section: Mineralogy Of Fe‐rich Oxygen‐bearing Ru–os Compoundssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The supergene origin of ruthenian hexaferrum in Ni‐laterites

et al. 2017

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“…Its composition suggests that the Sulawesi laurites, even the crystals found in contact with secondary silicates, were not affected by post-magmatic alteration, as observed in laurites associated with other ophiolitic chromitites [12,14,[57][58][59][60][61][62][63][64][65]. During the alteration processes, laurite released S that was replaced by Fe and O to form a fine intergrowth of native ruthenium and magnetite [61] or it has lost part of the Os and Ir to form Ru-rich laurite [14]. Therefore, we can use the analyzed laurite to model the mechanism of its crystallization at high temperature.…”

Section: Origin Of the Pgm In The Sulawesi Chromititesmentioning

confidence: 99%

Chromite Composition and Accessory Minerals in Chromitites from Sulawesi, Indonesia: Their Genetic Significance

2016

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Several chromite deposits located in the in the South and Southeast Arms of Sulawesi, Indonesia, have been investigated by electron microprobe. According to the variation of the Cr# = Cr/(Cr + Fe 3+ ), the chromite composition varies from Cr-rich to Al-rich. Small platinum-group minerals (PGM), 1-10 µm in size, occur in the chromitites. The most abundant PGM is laurite, which has been found included in fresh chromite or in contact with chlorite along cracks in the chromite. Laurite forms polygonal crystals, and it occurs as a single phase or in association with amphibole, chlorite, Co-pentlandite and apatite. Small blebs of irarsite (less than 2 µm across) have been found associated with grains of awaruite and Co-pentlandite in the chlorite gangue of the chromitites. Grains of olivine, occurring in the silicate matrix or included in fresh chromite, have been analyzed. They show a composition typical of mantle-hosted olivine. The bimodal composition and the slight enrichment in TiO 2 observed in some chromitites suggest a vertical zonation due to the fractionation of a single batch magma with an initial boninitic composition during its ascent, in a supra-subduction zone. This observation implies the accumulation of Cr-rich chromitites at deep mantle levels and the formation of the Al-rich chromitites close or above the Moho-transition zone. All of the laurites are considered to be magmatic in origin, i.e., entrapped as solid phases during the crystallization of chromite at temperature of around 1200˝C and a sulfur fugacity below the sulfur saturation. Irarsite possibly represents a low temperature, less than 400˝C, exsolution product.

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“…Primary magmatic PGM are laurite, erlichmanite, Os-Ir-Ru alloys, cooperite, Rh-pentlandite, kashinite, and Pt-Fe alloys. It is uncertain whether they are true PGE oxides, or correspond to a mixture of Ru-rich alloys and Fe oxide (magnetite) such as those found in Loma Peguera chromitite described by Zaccarini et al (2014). In particular, the secondary PGM assemblage consists of Ru-Os-Ir-Fe-O compounds, Pt-Pd-Fe-Ni-Cu-Co alloys, and potarite.…”

Section: Sample Provenance and Previous Workmentioning

confidence: 99%

Electron Microprobe and Raman Spectroscopy Investigation of an Oxygen-Bearing Pt–Fe–Pd–Ni–Cu Compound from Nurali Chromitite (Southern Urals, Russia)

et al. 2015

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One grain, about 100×80 μm in size, occurring in chromitite associated with the layered sequence of the Nurali mafic-ultramafic complex (Southern Urals, Russia) was investigated by electron-microprobe analyses and Raman spectroscopy. The grain is characterized by a spotty, rugged appearance and chemical zoning from which two compositions were calculated: (Pt(0.35)Pd(0.26)Fe(0.22)Cu(0.01)Ni(0.05))(0.98)O(1.02) and (Fe(0.90)Pt(0.58)Ni(0.28)Pd(0.13)Cu(0.08)Rh(0.01))(1.98)O(1.02). In the lack of X-ray data, Raman spectroscopy established the presence of a diffuse 500-700 band and a sharp peak at 657 cm⁻¹ of relative wavenumber that strongly resemble the Raman spectra of synthetic PtO and PdO (palladinite). It is concluded that the Nurali grain probably represents a platinum group element (PGE) oxide, and does not consist of a mixture of PGE alloys with Fe oxide or hydroxide as reported for other natural PGE-O compounds.

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Ruthenium and Magnetite Intergrowths From the Loma Peguera Chromitite, Dominican Republic, and Relevance to the Debate Over the Existence of Platinum-Group Element Oxides and Hydroxides

Cited by 11 publications

References 28 publications

The supergene origin of ruthenian hexaferrum in Ni‐laterites

The supergene origin of ruthenian hexaferrum in Ni‐laterites

Chromite Composition and Accessory Minerals in Chromitites from Sulawesi, Indonesia: Their Genetic Significance

Electron Microprobe and Raman Spectroscopy Investigation of an Oxygen-Bearing Pt–Fe–Pd–Ni–Cu Compound from Nurali Chromitite (Southern Urals, Russia)

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